When moving from one server to another, what you have to do is copy
the entire directory from the old machine to the new one. You should
use the same exact directory structure. Once you have done so, you can
run the install program and install the server to the same directory.
It will use your existing settings.
The only thing you will not have access to is the domain keys / DKIM
setting that you have previously set up. They are stored encrypted in
the database specific to the physical machine, so they must be added
to the new machine manually.
Once you have the second server running, you should go into the
original server and make sure the license is de-authorized there.